Image sensor device and method

ABSTRACT

A system and method for reducing cross-talk between photosensitive diodes is provided. In an embodiment a first color filter is formed over a first photosensitive diode and a second color filter is formed over a second photosensitive diode, and a gap is formed between the first color filter and the second color filter. The gap will serve to reflect light that otherwise would have crossed from the first color filter to the second color filter, thereby reducing cross-talk between the first photosensitive diode and the second photosensitive diode. A reflective grid may also be formed between the first photosensitive diode and the second photosensitive diode in order to assist in the reflection and further reduce the amount of cross-talk.

BACKGROUND

Complementary metal oxide semiconductor image sensors generally utilizea series of photodiodes formed within an array of pixel regions of asemiconductor substrate in order to sense when light has impacted thephotodiode. Adjacent to each of the photodiodes within each of the pixelregions a transfer transistor may be formed in order to transfer thesignal generated by the sensed light within the photodiode at a desiredtime. Such photodiodes and transfer transistors allow for an image to becaptured at a desired time by operating the transfer transistor at thedesired time.

The complementary metal oxide semiconductor image sensors may generallybe formed in either a front side illumination configuration or aback-side illumination configuration. In a front-side illuminationconfiguration light passes to the photodiode from the “front” side ofthe image sensor where the transfer transistor has been formed. However,in this configuration the light is forced to pass through metal layers,dielectric layers, and past the transfer transistor before it reachesthe photodiode. This may generate processing and/or operational issuesas the metal layers, dielectric layers, and the transfer transistor maynot necessarily be transparent and may block the light as it is tryingto reach the photodiode.

In a back-side illumination configuration, the transfer transistor, themetal layers, and the dielectric layers are formed on a the front sideof the substrate, and light is allowed to pass to the photodiode fromthe “back” side of the substrate such that the light hits the photodiodebefore it reaches the transfer transistor, the dielectric layers, or themetal layers. Such a configuration may reduce the complexity of themanufacturing of the image sensor and its operation.

However, pixel regions that are adjacent to each other may interferewith each other's operation in what is known as cross-talk. Suchcross-talk can reduce the precision and efficiency of the image sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an image sensor with an array of pixel regions inaccordance with an embodiment;

FIG. 2 illustrates a first photosensitive diode and a secondphotosensitive diode in a substrate in accordance with an embodiment;

FIG. 3 illustrates a formation of a reflective grid over the substratein accordance with an embodiment;

FIG. 4 illustrates a formation of a first color filter and a secondcolor filter with a gap therebetween in accordance with an embodiment;

FIG. 5 illustrates a deposition of material over the first color filterand the second color filter in accordance with an embodiment; and

FIG. 6 illustrates a formation of a microlens over the first colorfilter and the second color filter in accordance with an embodiment.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments are discussed in detail below. Itshould be appreciated, however, that the embodiments provide manyapplicable concepts that can be embodied in a wide variety of specificcontexts. The specific embodiments discussed are merely illustrative ofspecific ways to make and use the embodiments, and do not limit thescope of the embodiments.

Embodiments will be described with respect to a specific context, namelya complementary metal oxide semiconductor (CMOS) back side illuminatedimage sensor. Other embodiments may also be applied, however, to otherimage sensors and other semiconductor devices.

With reference now to FIG. 1, there is shown an image sensor 100 whichcomprises a grid or array of backside illuminated pixel regions 101. Theimage sensor 100 also may comprise a logic region 103 located adjacentto the array of pixel regions 101. The logic region 103 may haveadditional circuitry and contacts for input and output connections toand from the array of pixel regions 101. The logic region 103 isutilized to provide an operating environment for the pixel regions 101and to moderate communications between the array of pixel regions 101and other external devices (not shown).

FIG. 2 illustrates a simplified cross sectional view of adjacent pixelregions 101 through line A-A′ in FIG. 1, and shows a substrate 201 withtwo pixel regions 101 separated by isolation regions 205. The substrate201 may comprise a front side 202 and a back side 204 and may be asemiconductor material such as silicon, germanium, diamond, or the like,with a crystal orientation of (110). Alternatively, compound materialssuch as silicon germanium, silicon carbide, gallium arsenic, indiumarsenide, indium phosphide, silicon germanium carbide, gallium arsenicphosphide, gallium indium phosphide, combinations of these, and thelike, with other crystal orientations, may also be used. Additionally,the substrate 201 may comprise a silicon-on-insulator (SOI) substrate.Generally, an SOI substrate comprises a layer of a semiconductormaterial such as epitaxial silicon, germanium, silicon germanium, SOI,silicon germanium on insulator (SGOI), or combinations thereof. Thesubstrate 201 may be doped with a p-type dopant, such as boron, gallium,although the substrate may alternatively be doped with an n-type dopant,as is known in the art.

The isolation regions 205 may be located within the substrate 201between the individual pixel regions 101 in order to separate andisolate the pixel regions 101. The isolation regions 205 may be shallowtrench isolations generally formed by etching the substrate 201 to forma trench and filling the trench with dielectric material as is known inthe art. The isolation regions 205 may be filled with a dielectricmaterial such as an oxide material, a high-density plasma (HDP) oxide,or the like, formed by conventional methods known in the art.Optionally, an oxide liner may be formed along the sidewalls of theisolation regions 205.

Photosensitive diodes 207 may be formed in respective pixel regions 101.The photosensitive diodes 207 may be utilized to generate a signalrelated to the intensity or brightness of light that impinges on thephotosensitive diodes 207. In an embodiment the photosensitive diodes207 may comprise n-type doped regions 209 formed in the substrate 201(which in this embodiment may be a p-type substrate) and also maycomprise heavily doped p-type doped regions 211 formed on the surface ofthe n-type doped regions 209 to form a p-n-p junction.

The n-type doped regions 209 may be formed, e.g., using aphotolithographic masking and implantation process. For example, a firstphotoresist (not shown in FIG. 2) may be placed on the substrate 201.The first photoresist, may comprise a conventional photoresist material,such as a deep ultra-violet (DUV) photoresist, and may be deposited onthe surface of the substrate 201, for example, by using a spin-onprocess to place the first photoresist. However, any other suitablematerial or method of forming or placing the first photoresist mayalternatively be utilized. Once the first photoresist has been placed onthe substrate 201, the first photoresist may be exposed to energy, e.g.light, through a patterned reticle in order to induce a reaction inthose portions of the first photoresist exposed to the energy. The firstphotoresist may then be developed, and portions of the first photoresistmay be removed, exposing a portion of the substrate 201 where thephotosensitive diodes 207 are desired to be located.

Once the first photoresist has been placed and developed, the heavilydoped n-type doped regions 209 may be formed by implanting n-typedopants (e.g., phosphorous, arsenic, antimony, or the like) through thefirst photoresist. In an embodiment the n-type doped regions 209 may beimplanted such that their concentration of between about 1e15 atom/cm³and about 1e20 atom/cm³, such as about 8e15 atom/cm³. However, anysuitable alternative concentration for the heavily doped n-type dopedregions 209 may alternatively be utilized.

After the n-type doped regions 209 have been formed (e.g., through theimplantation process), the p-type doped regions 211 may be formed using,e.g., an ion implantation process using the first photoresist as a mask.The p-type doped regions 211 may be formed to extend into the substrate201 between about 1 μm and about 4 μm. Additionally, the p-type dopedregions 211 may be formed to have a concentration of between about 1e15atom/cm³ and about 5e19 atom/cm³, such as about 1e16 atom/cm³.

Once the photosensitive diodes 207 have been formed, the firstphotoresist may be removed. In an embodiment, the first photoresist maybe removed using a process such as ashing.

Further, as one of ordinary skill in the art will recognize, thephotosensitive diodes 207 described above are merely one type ofphotosensitive diodes 207 that may be used in the embodiments. Anysuitable photodiode may be utilized with the embodiments, and all ofthese photodiodes are intended to be included within the scope of theembodiments. Additionally, the precise methods or order of stepsdescribed above may be modified, such as by forming the p-type dopedregions 211 prior to the formation of the n-type doped regions 209,while still remaining within the scope of the embodiments.

A first transistor 213 and a second transistor 215 may be formed inrespective pixel regions 101 adjacent to their respective photosensitivediodes 207. The first transistor 213 and the second transistor 215 maybe transfer transistors. However, the first transistor 213 and thesecond transistor 215 are also merely representative of the many typesof functional transistors that may be utilized within the pixel regions101. For example, while the first transistor 213 and the secondtransistor 215 are illustrated in FIG. 2 as transfer transistors,embodiments may additionally include other transistors located withinthe pixel regions 101, such as reset transistors, source followertransistors, or select transistors. These transistors may be arranged,for example, to form a four transistor CMOS image sensor (CIS). Allsuitable transistors and configurations that may be utilized in an imagesensor are fully intended to be included within the scope of theembodiments.

The first transistor 213 and the second transistor 215 may comprise gatestacks that may be formed over the substrate 201. The gate stacks mayeach comprise a gate dielectric 217 and a gate electrode 219. The gatedielectrics 217 and gate electrodes 219 may be formed and patterned onthe substrate 201 by any suitable process known in the art. The gatedielectrics 217 may be a high-K dielectric material, such as siliconoxide, silicon oxynitride, silicon nitride, an oxide, anitrogen-containing oxide, aluminum oxide, lanthanum oxide, hafniumoxide, zirconium oxide, hafnium oxynitride, a combination thereof, orthe like. The gate dielectrics 217 may have a relative permittivityvalue greater than about 4.

In an embodiment in which the gate dielectrics 217 comprise an oxidelayer, the gate dielectrics 217 may be formed by any oxidation process,such as wet or dry thermal oxidation in an ambient comprising an oxide,H₂O, NO, or a combination thereof, or by chemical vapor deposition (CVD)techniques using tetra-ethyl-ortho-silicate (TEOS) and oxygen as aprecursor. In one embodiment, the gate dielectrics 217 may be betweenabout 10 Å to about 150 Å in thickness, such as 100 Å in thickness.

The gate electrodes 219 may comprise a conductive material, such as ametal (e.g., tantalum, titanium, molybdenum, tungsten, platinum,aluminum, hafnium, ruthenium), a metal silicide (e.g., titaniumsilicide, cobalt silicide, nickel silicide, tantalum silicide), a metalnitride (e.g., titanium nitride, tantalum nitride), dopedpoly-crystalline silicon, other conductive materials, or a combinationthereof. In one example, amorphous silicon is deposited andrecrystallized to create poly-crystalline silicon (poly-silicon). In anembodiment in which the gate electrodes 219 is poly-silicon, the gateelectrodes 219 may be formed by depositing doped or undoped poly-siliconby low-pressure chemical vapor deposition (LPCVD) to a thickness in therange of about 100 Å to about 2,500 Å, such as 1,200 Å.

Spacers 221 may be formed on the sidewalls of the gate dielectrics 217and the gate electrodes 219. The spacers 221 may be formed by blanketdepositing a spacer layer (not shown) on the previously formedstructure. The spacer layer may comprise SiN, oxynitride, SiC, SiON,oxide, and the like, and may be formed by commonly used methods such aschemical vapor deposition (CVD), plasma enhanced CVD, sputter, and othermethods known in the art. The spacer layer is then patterned to form thespacers 221, such as by anisotropically etching to remove the spacerlayer from the horizontal surfaces of the structure.

Source/drain regions 223 may be formed in the substrate 201 on anopposing side of the gate dielectrics 217 from the photosensitive diodes207. In an embodiment in which the substrate 201 is a p-type substrate,the source/drain regions 223 may be formed by implanting appropriaten-type dopants such as phosphorous, arsenic or antimony. Thesource/drain regions 223 may be implanted using the gate electrodes 219and the spacers 221 as masks to form lightly doped source/drain (LDD)regions 225 and heavily doped source/drain regions 227.

It should be noted that one of ordinary skill in the art will realizethat many other processes, steps, or the like may be used to form thesource/drain regions 223 and the photosensitive diodes 207. For example,one of ordinary skill in the art will realize that a plurality ofimplants may be performed using various combinations of spacers andliners to form the source/drain regions 223 and the photosensitivediodes 207 having a specific shape or characteristic suitable for aparticular purpose. Any of these processes may be used to form thesource/drain regions 223 and the photosensitive diodes 207, and theabove description is not meant to limit the embodiments to the stepspresented above.

Once the first transistor 213 and the second transistor 215 have beenformed, a first inter-layer dielectric (ILD) layer 228 may be formedover the pixel regions 101 and contacts 229 may be formed through thefirst ILD layer 228. The first ILD layer 228 may comprise a materialsuch as boron phosphorous silicate glass (BPSG), although any suitabledielectrics may be used for either layer. The first ILD layer 228 may beformed using a process such as PECVD, although other processes, such asLPCVD, may alternatively be used. The first ILD layer 228 may be formedto a thickness of between about 100 Å and about 3,000 Å.

The contacts 229 may be formed through the first ILD layer 228 withsuitable photolithography and etching techniques. In an embodiment afirst photoresist material is utilized to create a patterned mask todefine contacts 229. Additional masks, such as a hardmask, may also beused. An etching process, such as an anisotropic or isotropic etchprocess, is performed to etch the first ILD layer 228.

Contacts 229 may then be formed so as to contact the substrate 201 andthe gate electrodes 219. The contacts 229 may comprise abarrier/adhesion layer (not individually shown in FIG. 2) to preventdiffusion and provide better adhesion for the contacts 229. In anembodiment, the barrier layer is formed of one or more layers oftitanium, titanium nitride, tantalum, tantalum nitride, or the like. Thebarrier layer may be formed through chemical vapor deposition, althoughother techniques could alternatively be used. The barrier layer may beformed to a combined thickness of about 50 Å to about 500 Å.

The contacts 229 may be formed of any suitable conductive material, suchas a highly-conductive, low-resistive metal, elemental metal, transitionmetal, or the like. In an exemplary embodiment the contacts 229 areformed of tungsten, although other materials, such as copper, couldalternatively be utilized. In an embodiment in which the contacts 229are formed of tungsten, the contacts 229 may be deposited by CVDtechniques known in the art, although any method of formation couldalternatively be used.

After the contacts 229 are formed, further processing of the front side202 of the substrate 201 may be performed. This processing may compriseforming various conductive and dielectric layers (collectively referredto in FIG. 2 by the reference number 231) in order to forminterconnections between the individually formed devices to each other.These interconnections may be made through any suitable formationprocess (e.g., lithography with etching, damascene, dual damascene, orthe like) and may be formed using suitable conductive materials such asaluminum alloys, copper alloys, or the like.

Additionally, once the interconnections have been formed over the firstILD layer 228, a passivation layer 233 may be formed in order to protectthe underlying layers from physical and chemical damage. The passivationlayer 233 may be made of one or more suitable dielectric materials suchas silicon oxide, silicon nitride, low-k dielectrics such as carbondoped oxides, extremely low-k dielectrics such as porous carbon dopedsilicon dioxide, combinations of these, or the like. The passivationlayer 233 may be formed through a process such as chemical vapordeposition (CVD), although any suitable process may be utilized.

FIG. 3 illustrates a placement of the substrate 201 on a carrier wafer307 and further processing on the back side 204 of the substrate 201that may be performed after the processing on the front side 202 of thesubstrate 201. The carrier wafer 307 may be utilized to provide supportand protection to the structures on the front side 202 of the substrate201 while the back side 204 is further processed, and the carrier wafer307 may comprise a material such as glass, silicon, glass ceramics,combinations of these, or the like. The substrate 201 may be attached tothe carrier wafer 307 using, e.g., an adhesive (not individuallyillustrated in FIG. 3), although any suitable method of attaching thesubstrate 201 to the carrier wafer 307 may alternatively be utilized.

Alternatively, the substrate 201 may be wafer bonded to another wafer(not illustrated) instead of the carrier wafer 307. In this embodimentthe substrate 201 may be physically and electrically connected throughthe conductive and dielectric layers 231 and the passivation layer 233to another wafer in order to provide signals and/or power between thesubstrate 201 and the other wafer. This and any other method ofprotecting the front side 202 of the substrate 201 may alternatively beutilized, and all such methods are fully intended to be included withinthe scope of the embodiment.

Once the substrate 201 has been placed on the carrier wafer 307, theback side 204 of the substrate 201 may be processed further. In anembodiment the thickness of the back side 204 of the substrate 201 mayreduced, or thinned. Thinning reduces the distance that light travelsthrough the back side 204 of the substrate 201 before it reaches thephotosensitive diodes 207. The thinning of the back side 204 of thesubstrate 201 may be performed using a removal process such as chemicalmechanical polishing (CMP). In a CMP process, a combination of etchingmaterials and abrading materials are put into contact with the back side204 of the substrate 201 and a grinding pad (not shown) is used to grindaway the back side 204 of the substrate 201 until a desired thickness isachieved. However, any suitable process for thinning the back side 204of the substrate 201, such as etching or a combination of CMP andetching, may alternatively be used. The back side 204 of the substrate201 may be thinned so that the substrate 201 has a thickness of betweenabout 2 μm and about 2.3 μm.

FIG. 3 also illustrates the formation of a reflective grid 301 over theback side 204 (now thinned) of the substrate 201. In an embodiment thereflective grid 301 may be used to ensure that light has entered theimage sensor 100 over one pixel region 101 does not cross into anotherpixel region 101 prior to impinging upon a photosensitive diode 207. Assuch, the reflective grid 301 may be formed between the individual pixelregions 101 over the isolation regions 205 in the image sensor 100.

In an embodiment the reflective grid 301 may be formed by initiallyforming a holding layer 303 to hold the reflective grid 301. In anembodiment the holding layer 303 may comprise a transparent materialthat will allow the passage of light through the holding layer 303, suchas an oxide. For example, the holding layer 303 may be a material suchas silicon oxide, although any other suitable material may alternativelybe utilized. The holding layer 303 may be formed through a process suchas CVD, PECVD, thermal oxidation or combinations of these. The holdinglayer 303 may be formed to a thickness greater than the desiredthickness of a reflective grid 301 (discussed further below with respectto FIG. 3).

Once the holding layer 303 is in place, the reflective grid 301 may beformed by initially forming openings within the holding layer 303. Theopenings may be formed using, e.g., a suitable photolithographic maskingand etching process. In such a process a second photoresist (not shownin FIGS. 3) may be placed on the holding layer 303. The secondphotoresist may comprise a conventional photoresist material, such as adeep ultra-violet (DUV) photoresist, and may be deposited on the surfaceof the holding layer 303, for example, by using a spin-on process toplace the second photoresist. However, any other suitable material ormethod of forming or placing the second photoresist may alternatively beutilized. Once the second photoresist has been placed on the holdinglayer 303, the second photoresist may be exposed to energy, e.g. light,through a patterned reticle in order to induce a reaction in thoseportions of the second photoresist exposed to the energy. The secondphotoresist may then be developed, and portions of the secondphotoresist may be removed, exposing a surface of the holding layer 303where the reflective grid 301 is desired.

Once the second photoresist is in place, portions of the holding layer303 may be removed to form the openings and to make room for thereflective grid 301. In an embodiment in which the holding layer 303 issilicon oxide, the removal may be performed using a suitable etchingprocess, such as an anisotropic etch using an etchant such as ammoniumfluoride/hydrogen fluoride or ammonium fluoride/acetic acid, althoughany other suitable removal process may be alternatively utilized. Theopenings may be formed to have a first width w₁ that is greater than asubsequently formed gap 407 (not illustrated in FIG. 3 but illustratedand discussed below with respect to FIG. 4). In an embodiment in whichthe gap 407 has a second width w₂ of about 0.1 μm, the openings may beformed to have a first width w₁ of greater than about 0.1 μm, such as0.15 μm.

Once the openings have been formed, the openings may be filled withreflective material to form the reflective grid 301. In an embodimentthe reflective material may be a metal material, such as aluminum (Al),copper (Cu), tantalum (Ta), titanium nitride (TiN) or combinations ofthese, although any other suitable reflective material may alternativelybe utilized. In an embodiment the reflective material may be placedwithin the openings by first filling and overfilling the openings withthe reflective material using a suitable deposition process, such asCVD, PECVD, ALD, electroplating, electroless plating, combinations ofthese, or the like. Once the reflective material has filled andoverfilled the openings, excess amounts of the reflective materialoutside of the openings may be removed and the reflective material maybe planarized with the holding layer 303. In an embodiment the removaland the planarization may be performed using a suitable planarizationtechnique such as chemical mechanical polishing (CMP). The reflectivegrid 301 may be formed to have a first height h₁ of between about 100 ∈and about 10000 Å, such as about 4000 Å.

After the reflective grid 301 has been formed within the openings of theholding layer 303, a covering layer 305 may be formed over thereflective grid 301 to encapsulate the reflective grid 301 within theholding layer 303. In an embodiment the covering layer 305 may be asimilar material as the holding layer 303 (e.g., a translucent materialsuch as silicon oxide), and may be formed through a deposition processsuch as CVD, PECVD, combinations of these, or the like. The coveringlayer 305 may have a thickness of between about 100 Å and about 10000 Å,such as about 6000 Å.

FIG. 4 illustrates the formation of a first color filter 401 and asecond color filter 403 on the back side 204 of the substrate 201 overthe reflective grid 301. The first color filter 401 and the second colorfilter 403 may comprise filters for one of the primary colors (e.g.,red, green, blue) and may be positioned to filter the light that willimpinge upon the photosensitive diodes 207. The first color filter 401and the second color filter 403 may be part of an array pattern of colorfilters, with each color filter being located over a respective one ofthe pixel regions 101. For example, the first color filter 401 and thesecond color filter 403 may be part of a Bayer RGB pattern, a YotsubaCRGB pattern, or any other suitable pattern for the location of colorfilters over an image sensor 100.

The first color filter 401 and the second color filter 403 may comprisea polymeric material or resin, such as a polymeric polymer, whichincludes colored pigments. In an embodiment in which a polymeric polymeris utilized to form the first color filter 401, the first color filter401 may be formed over one photosensitive diode 207 using a process suchas spin coating to form a first blanket layer of the first polymericpolymer, although any other suitable method may alternatively beutilized.

Once the first blanket layer of the polymeric polymer has been formed,the first blanket layer may be patterned such that the first colorfilter 401 is formed over the desired pixel region 101. In an embodimentthe first blanket layer may be patterned using a suitablephotolithographic masking and etching process, wherein a thirdphotoresist (not illustrated in FIG. 4) is placed, exposed, anddeveloped to cover the desired portions of the first blanket layer. Thethird photoresist may be similar to the second photoresist describedabove. Once the desired portions are protected, the exposed portions ofthe first blanket layer may be removed using, e.g., an anisotropic etch.

The second color filter 403 may be formed to filter light from otherpixel regions 101 than the first color filter 401 (such as the adjacentpixel region 101 as illustrated in FIG. 4). In an embodiment the secondcolor filter 403 may be formed by initially spin coating or otherwiseplacing a second blanket layer (not illustrated in FIG. 4) of thematerial for the second color filter 403. Once the second blanket layer403 has been formed, the second blanket layer may be patterned such thatthe second color filter 403 is formed over the desired pixel region 101.In an embodiment the second blanket layer may be patterned using asuitable photolithographic masking and etching process, wherein a fourthphotoresist (not illustrated in FIG. 4) is placed, exposed, anddeveloped to cover the desired portions of the second blanket layer. Thefourth photoresist may be similar to the second photoresist describedabove. Once the desired portions are protected, the exposed portions ofthe second blanket layer may be removed using, e.g., an anisotropicetch.

FIG. 4 also illustrates the formation of a gap 407 that may be formedbetween the first color filter 401 and the second color filter 403. Thegap 407 may be formed by adjusting the second photoresist and the thirdphotoresist during the patterning of the first color filter 401 and thesecond color filter 403 so that those portions of the first blanketlayer and the second blanket layer that are located where the gap 407 isdesired are removed to leave behind the gap 407 (which may be filledwith an ambient gas such as air) between the first color filter 401 andsecond color filter 403. For example, in an embodiment in which the gap407 may have a second width w₂ between about 0.01 μm and about 1 μm,such as about 0.1 μm, the width of the first color filter 401 and thesecond color filter 403 may each be reduced by 0.05 μm per side suchthat, together, there is 0.1 μm between them, thereby forming the gap407 once the first color filter 401 and the second color filter 403 havebeen patterned.

By placing the gap 407 between the first color filter 401 and the secondcolor filter 403, the gap 407 may be used as a light guide to reflectlight passing through either the first color filter 401 or the secondcolor filter 403. While the individual color filters may have similarrefractive indexes (such that large angles of injection may put light ona path to cross between the color filters), the inclusion of the gap 407interrupts this similarity in refractive indexes and helps to reflectthe incoming light. By reflecting the incoming light from passingthrough the gap 407, cross-talk between adjacent pixel regions 101 maybe reduced. As such, the overall efficiency of the image sensor 100 maybe improved.

FIG. 5 illustrates a formation of a gap covering layer 501 over thefirst color filter 401 and the second color filter 403 and partiallywithin the gaps 407. In an embodiment the gap covering layer 501 may bea transparent material that allows light to pass through it, and may be,e.g., silicon oxide, although any suitably transparent material mayalternatively be utilized. The gap covering layer 501 may be formedusing a deposition process such as CVD or PECVD, or the like, and may beformed to a thickness over the first color filter 401 and the secondcolor filter 403 of between about 50 Å and about 5000 Å, such as about500 Å.

By controlling the deposition process used to form the gap coveringlayer 501 over the first color filter 401 and the second color filter403, the material of the gap covering layer 501 (e.g., silicon oxide)will deposit non-conformably within the gap 407 and will build up on thecorners of the gap 407 faster than along the sidewalls and the bottom ofthe gap 407. This process leads to the formation of an overhang and, asthe deposition process continues, the overhangs will merge, therebysealing off the gap 407 with the ambient still inside a part of the gap407. For example, in an embodiment in which the gap covering layer 501is silicon oxide deposited by CVD, the CVD process may be performed withprecursors such as silane and oxygen at a temperature of between about50° C. and about 500° C., such as about 200° C., and a pressure ofbetween about 0.1 for and about 100 torr, such as about 10 torr

FIG. 6 illustrates the formation of microlenses 601 over the gapcovering layer 501. The microlenses 601 may be formed opposite the gapcovering layer 501 from the substrate 201, and may be used to focusimpinging light more directly onto the photosensitive diodes 207. Themicrolenses 601 may be formed by first applying and patterning apositive type photoresist (not shown) over the gap covering layer 501.Once formed, the patterned photoresist may then be baked to round thephotoresist into the curved microlenses 601.

By forming the gap 407 between the pixel regions 101 in the image sensor100, light that impinges on the gap 407 may be reflected back towardsthe appropriate photosensitive diode 207, making the image sensor 100more efficient at capturing light and reducing or eliminating cross-talkbetween different pixel regions 101. With the addition of the reflectivegrid 301, the reflective grid 301 and the gap 407 will work inconjunction with one another to reflect even more light towards thecorrect photosensitive diode 207. By ensuring that the light impingesupon the correct photosensitive diode 207, the overall image sensor 100will be more efficient.

In accordance with an embodiment, a semiconductor device comprising animage sensor comprising a first pixel region and a second pixel regionin a substrate, the first pixel region being adjacent to the secondpixel region, is provided. A first color filter is over the first pixelregion and a second color filter is over the second pixel region. A gapis between the first color filter and the second color filter.

In accordance with another embodiment, a semiconductor device comprisinga substrate with a first side and a second side, the substratecomprising a first photosensitive diode and a second photosensitivediode, is provided. A reflective grid is located over the substratebetween the first photosensitive diode and the second photosensitivediode, and a first color filter and a second color filter on an oppositeside of the reflective grid than the substrate. A gap is over thereflective grid and between the first color filter and the second colorfilter.

In accordance with yet another embodiment, a method of manufacturing asemiconductor device comprising forming a first photosensitive diode anda second photosensitive diode in a substrate, the first photosensitivediode and the second photosensitive diode being in adjacent pixelregions, is provided. A first color filter blanket layer is formed overthe substrate, and a first portion of the first color filter blanketlayer is removed to form a first color filter over the firstphotosensitive diode. A second color filter blanket layer is formed overthe substrate, and a second portion of the second color filter blanketlayer is removed to form a second color filter over the secondphotosensitive diode, the removing the first portion and the removingthe second portion forming an opening in a region adjacent both thefirst color filter and the second color filter.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the embodiments as defined by the appendedclaims. For example, charge coupled devices (CCD) may be utilized inplace of the CMOS devices within the image sensor, and the image sensormay be a front side image sensor instead of a back side image sensor.These devices, steps and materials may be varied while remaining withinthe scope of the embodiments.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the embodiments, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to theembodiments. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

What is claimed is:
 1. A semiconductor device comprising: an imagesensor comprising a first pixel region and a second pixel region in asubstrate, the first pixel region being adjacent to the second pixelregion and also being adjacent to a first side of the substrate; a firstcolor filter over the first pixel region, wherein the color filter islocated adjacent to a second side of the substrate opposite the firstside of the substrate; a second color filter over the second pixelregion; a gap between the first color filter and the second colorfilter, wherein the gap is void of solid material; and a gap coveringlayer over the first color filter and the second color filter, whereinthe gap covering layer is a single material and also extends into aregion between the first color filter and the gap, and covers a sidewallof the first color filter from a top of the first color filter to abottom of the first color filter.
 2. The semiconductor device of claim1, wherein the single material is a transparent solid material.
 3. Thesemiconductor device of claim 2, wherein the single material is siliconoxide.
 4. The semiconductor device of claim 2, wherein the singlematerial has a thickness over the first color filter of between about 50Å and about 5000 Å.
 5. The semiconductor device of claim 1, furthercomprising a reflective grid between the gap and the substrate.
 6. Thesemiconductor device of claim 5, wherein the reflective grid is a metalgrid.
 7. The semiconductor device of claim 5, wherein the reflectivegrid is encapsulated by a support layer.
 8. The semiconductor device ofclaim 1 further comprising a microlens over the first color filter. 9.The semiconductor device of claim 1, wherein the semiconductor device isa back side illuminated image sensor.
 10. A semiconductor devicecomprising: a substrate with a first side and a second side, thesubstrate comprising a first photosensitive diode and a secondphotosensitive diode in the first side; a reflective grid located overthe second side of the substrate between the first photosensitive diodeand the second photosensitive diode, wherein the reflective grid isencapsulated within a holding layer, the holding layer being a singlematerial and being in contact with a top, a bottom, and a sidewall ofthe reflective grid; a first color filter and a second color filterdisposed over the second side of the substrate; and a gap over thereflective grid and between the first color filter and the second colorfilter, wherein the gap is void of solid material; a gap encapsulatinglayer covering a sidewall of the first color filter from a top of thefirst color filter to a bottom of the first color filter, wherein thegap encapsulating material comprises a single material throughout thegap encapsulating layer; and a lens over the first color filter.
 11. Thesemiconductor device of claim 10, wherein the reflective grid is a metalgrid.
 12. The semiconductor device of claim 10, wherein the singlematerial has a thickness over the first color filter of between about 50Å and about 5000 Å.
 13. The semiconductor device of claim 10, whereinthe single material is an oxide.
 14. The semiconductor device of claim10, wherein the semiconductor device is a back side illuminated imagesensor.
 15. A semiconductor device comprising: a first color filter; asecond color filter laterally separated from the first color filter by afirst region, wherein neither the first color filter nor the secondcolor filter extend into the first region and the first region is voidof solid material; an encapsulating material encapsulating the firstregion, wherein the encapsulating material is a single material thatfully surrounds the first region; a reflective grid under the firstcolor filter and the second color filter, wherein the reflective gridhas a top surface facing towards the first color filter, a bottomsurface facing away from the first color filter, and a sidewall that areall in contact with a first material; and a first photosensitive diodeand a second photosensitive diode located under the reflective grid on afirst side of a substrate, wherein the reflective grid is locatedadjacent to an opposite side of the substrate.
 16. The semiconductordevice of claim 15, wherein the reflective grid is a metal grid.
 17. Thesemiconductor device of claim 15, wherein the encapsulating material isan oxide.
 18. The semiconductor device of claim 15, wherein thereflective grid is encapsulated by a holding layer.
 19. Thesemiconductor device of claim 15, wherein the semiconductor device is aback side illuminated image sensor.
 20. The semiconductor device ofclaim 15, wherein the encapsulating material is a transparent material.